Walls: I volunteered years ago in the rare-books collection at the Baylor University library in Texas. I got bitten by the bug then. It's a very small field and a young one. You could probably put every preservation person in the U.S. in one large hotel ballroom. Most people who do this work are in academic settings or private libraries, but there are government libraries, too, beyond the Library of Congress. You've got the National Library of Medicine, for example.

Q. What are the challenges of carrying out the agency's mission without paper?

Wallis: The paper publication had a physical form, so there was some intellectual control over what it was and where you could find it. You could sit there for quite a long time without worrying about it becoming obsolete. You weren't going to go into the library one day and find out that a publication was inaccessible because it was in a different file format.

With digital, you have the whole issue of how do you know it's authentic? That all the information is there? The digital publication requires almost constant vigilance.